Multiaxis joint, especially artificial knee joint

ABSTRACT

A lower platform and an upper platform are connected first and second levers having different lengths, each lever being articulated about a first axis on said lower platform and a second axis on said upper platform. The upper platform can be swiveled from a rest position to a position of maximum excursion relative to the lower platform so that the distance between platforms is immediately reduced upon swiveling from the rest position. At least one axis is provided with a brake which slows down rotational movement.

PRIORITY CLAIM

This is a U.S. national stage of application No. PCT/DE00/04180, filedon Nov. 24, 2000. Priority is claimed on that application and on thefollowing applications: Country: Germany, Application No.: 199 61 915.8,Filed: Dec. 21, 1999; Country: Germany, Application No.: 100 26 440.9,Filed: May 29, 2000.

BACKGROUND OF THE INVENTION

The invention relates to a multiaxis joint, especially an artificialknee joint, whose axes of rotation are perpendicular to one plane.

DESCRIPTION OF THE RELATED ART

In prosthetics, artificial knee joints are known which swivel about asingle axis, their respective swiveling movement being unsatisfactory,and which in particular permit only an unnatural gait pattern. Multiaxisknee joints have therefore been disclosed whose axes are perpendicularto one plane, for example in accordance with U.S. Pat. No. 5,314,498.

In multiaxis knee joints of this type, a polar curve describes therelative movement of the instantaneous center of rotation duringswiveling. In this way, a harmonious gait pattern is obtained, becausewalking on uneven surfaces and stepping over small obstacles and thelike is made easier by a shortening of the knee joint. To do this, theleg has to be consciously lifted and, in the process, the instantaneouscenter of rotation generally shifts forward before the joint comes intothe actual flexion angle. In this forwardly directed movement, thepoints of articulation move away from one another, which results in alengthening of the knee joint. One reason for this, among others, isthat the polar curve and thus the instantaneous center of rotationgenerally lies outside the actual knee joint. In this respect, anunnatural pattern of movement is also produced here, because the legwhich is actually to be shortened is first lengthened and must thereforebe lifted higher than an obstacle or the normal pattern of movementactually requires.

SUMMARY OF THE INVENTION

Against this technical background, the invention has the object ofmaking available a multiaxis joint, especially an artificial knee joint,which permits a harmonious gait modeled after the natural function of aknee.

To achieve this object in a multiaxis joint, especially an artificialknee joint, whose axes of rotation are perpendicular to one plane, arelative swiveling of an upper platform toward a lower platform from arest position to a position of maximum excursion is permitted, uponwhich swiveling the distance between the platforms is immediatelyreduced with an excursion from the rest position. The polar curve whichdescribes the relative movement of the instantaneous center of rotationwill as a result also immediately describe a convergence of the twoplatforms which are attached to a thigh and lower leg, respectively.Thus, upon a walking movement and a lifting of the prosthesis, thedistance between a ground surface and a foot of the prosthesis isimmediately increased to such an extent that irregularities and smallobstacles can be surmounted in an almost natural way.

In particular, it is also provided for here that, during the swivelingof the platforms relative to one another, the instantaneous center ofrotation at all times lies inside the actual joint.

Here, the platforms are each understood to be an attachment elementwhich serves to bind the joint according to the invention to a femoralstump and to a below-knee prosthesis, respectively. In this respect, thespatial configuration of the platforms is open.

In terms of construction, provision can be made for the joint to bedesigned to be self-retaining or self-locking in the rest positionand/or the position of maximum excursion, or for these positions to bemarked by dead-point positions of the joint. This affords the advantage,in particular in the rest position, that the joint is as it were lockedin the respective position even when loaded. This results, on the onehand, in a stable and unstressed stance and, on the other hand, bucklingof the joint upon heel contact in the walking cycle is avoided. In thisrespect, a particular aim is to inhibit the joint in a range ofexcursion from one of the positions of between 0° and 10°. Nevertheless,initiation of the flexion phase starting from the rest position, inparticular also starting at 0°, is possible without any problem.

Alternatively, or in addition, provision can be made for the restposition and/or the position of maximum excursion to be fixed by one ormore limit stops. Such limit stops guarantee that the swiveling can takeplace only within a predetermined angle range. By means of a limit stop,it is also possible for a considerably greater load to be taken up bythe joint in said positions. It has proven expedient to provide for acushioned run-in into the rest position and/or the position of maximumexcursion. In this connection, it is conceivable on the one hand toprovide special dampers, for example also on limit stops, or in someother way to reduce the angular velocity of the axes of rotation duringthe run-in into the positions. A cushioned, gentle run-in into one ofthe positions can also be achieved by the predetermined kinematics ofthe joint itself, for example by the run-in into self-retaining,self-locking areas or dead-point positions.

In terms of construction, provision is made for the platforms to beconnected by two levers of different length articulated respectively attheir ends on the platforms.

This measure ensures that the upper platform is displaced variably notonly in height relative to the lower, but that the platforms areactually swiveled about an angle relative to one another. As a furtherconstruction measure, provision can be made that in one position, inparticular in the rest position, the opening angle of the linesconnecting the axes of the levers is less than 95°, and in particularthese can also be approximately perpendicular to one another. In thisrespect, it is preferable that, in this position in particular, an axisof the second lever is arranged lying substantially on the connectingline of the axes of a first lever. A setting of the joint is thusobtained such that in normal standing, when the joint assumes the restposition, a stable and unstressed stance is guaranteed. This up to andincluding a certain excursion, if loading takes place in this excursion.

In this respect, it is also preferably provided that, during theswiveling, the levers cross each other, or at least in continuation theconnecting lines of the first and second axes. These measures ensure,inter alia, that the instantaneous center of rotation during swivelinglies inside the joint according to the invention and that, as aconsequence, an approximately natural pattern of movement is obtained.

In a further embodiment, it is provided that in one position, inparticular in the rest position, the first axes of the leversarticulated on the lower platform are arranged substantially at the sameheight or, alternatively, that a first axis of a lever articulated onthe lower platform is arranged lying higher than the first axis of theother lever. Opposite the plane spanned by these two first axes in oneposition, in particular in the rest position, an angle of between 45°and 75°, in particular of between 50° and 60°, is preferably spannedbetween the first lever and this plane. This is the angle between theline connecting the axes of the first lever and the line connecting thefirst axes in the lower platform.

These construction measures are geared toward the natural attachment ofthe cruciate ligaments to the lower leg, and the natural articulation ofthe anterior cruciate ligament on the lower leg in the standingposition. Corresponding to the distance between the attachment ofanterior and posterior cruciate ligament to the lower leg, it is alsopreferably provided that the distance between the first axes is between36 mm and 62 mm. Likewise, the distance of the first axis from thesecond axis of the first lever articulated on the upper platform can bebetween 45 mm and 80 mm, once again geared toward the length of ananterior cruciate ligament between thigh and lower leg of a person ofaverage height. Corresponding to the distance between the attachment ofthe cruciate ligaments to the thigh, a distance between the second axesof between 16 mm and 46 mm is provided. The simulation of the human kneein respect of the cruciate ligaments is completed by the fact that,corresponding to the length of the posterior cruciate ligament, thedistance of the first axis from the second axis of the second leverarticulated on the upper platform is between 27 mm and 62 mm.

As a result of these construction measures, the situation is alsoachieved that in the rest position, i.e. in the standing position, theline of the principally vertical loading of the joint extends lyingpreferably between the two upper axes, and possibly also slightly infront of the second axis of the second lever, viewed in the direction ofswiveling, but which line is actually crossed by the levers.

Corresponding to the natural movement, a restriction on the excursion ofthe joint is also provided by means of corresponding dead-pointpositions or limit stops at between 130° and 175°.

To ensure a sufficient stability of the knee joint according to theinvention, in particular in the rest position, it is possible, as afurther construction measure, to provide for one lever to be designed asa double lever. This can be the first or the second lever, or, ifappropriate, both levers can be designed as double levers at the end ofa common shaft for example. Such a joint then satisfies the moststringent loading requirements.

In a preferred embodiment, the joint according to the invention isprovided with a counterrecoil mechanism which, when the loading of thejoint is released, for example when the leg is lifted, initiates anaturally acting swivel movement. Such a counterrecoil mechanism isgenerally arranged between upper and lower platform, so that any forcesarising only impact there.

It is expedient, in the rest position, to bind the counterrecoilmechanism vertically between the axes of the upper platform. There issufficient space available there for construction measures, and forceintroduction there is also favorable for excursion of the joint as aresult of the lever arrangements.

In a construction embodiment, it is provided that at least one lever ofthe counterrecoil mechanism is articulated on a shoulder protruding fromthe upper platform. As a result of this measure, the lever, even uponswiveling of the joint, is free from the upper platform. The latter mayalso have recesses for the at least one lever of the counterrecoilmechanism, so that the excursion needed for the joint is guaranteed. Tobe able to take account of individual requirements, the distance of theaxis of the articulation from the upper platform is expedientlyadjustable.

On the lower platform, the counterrecoil mechanism is preferably boundin a central seat via the guidance of an axially spring-mounted piston,which piston has the at least one lever articulated at its free enddirected toward the second platform. It is further preferred for thepiston to be guided on a normal axis, which extends substantiallyvertically in the rest position.

For at least one axis, a brake can further be provided for slowing downa rotational movement about this axis. In the joint according to theinvention, the braking of a single axis is generally sufficient sincethe axes are connected to one another in the manner of a joint chain.

A brake is preferred, for which independent protection is also required,in which the braking force is generated by a weight loading the joint.In the rest position in particular, the joint is then as it were lockedand ensures a very stable, comfortable stance, since in this stationaryrest position the loading from the body weight is at its greatest.

In a construction embodiment, it is provided that the axis is guided ina mounting which has a longitudinal slit. In the manner of known beltbrakes, braking is obtained by closure of the longitudinal slit and thusfrictional gripping of the axis. This embodiment of a brake, inparticular for the joint according to the invention, has the advantagethat it takes up very little space.

It has proven expedient to allow the weight to act on the mounting ofthe axis via a lever arm, in particular via a lever arm whose activelever arm length is adjustable, that is to say in particular that thesite of introduction of force into the lever arm is adjustable. It mayalso be conceivable actually to design the physical length of the leverarm so that it is variable,

for example by turning it in a thread. It is further preferred that theweight acts counter to the force of a spring. As a result of thesemeasures, the response of the brake and the brake operation itself canbe optimally adapted to the requirements of the prosthesis wearer.

In particular, it is further provided that in one position, inparticular in the rest position, a brake force can be preset so as totake account of the individual requirements of a prosthesis wearer bymaking it possible to preset the force needed for excursion inparticular from the rest position.

The joint according to the invention is first explained in greaterdetail on the basis of a functional model represented in the drawing,which functional model does not reveal the actual configuration as aknee joint in the prosthesis. Thereafter, a preferred illustrativeembodiment of a joint, with counterrecoil mechanism and brake, shown inthe rest position, is discussed in more detail. In the drawing:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the functional model in a rest position, FIG. 2 shows thefunctional model with a 60° excursion of the upper platform relative tothe lower platform,

FIG. 3 shows a maximum excursion of the functional model of 140°,

FIG. 4 shows a diagram to illustrate the patterns of movement,

FIG. 5 shows a preferred illustrative embodiment of a joint according tothe invention, in a position and view corresponding to FIG. 1,

FIG. 6 shows a view of the joint according to the arrow VI in FIG. 5,

FIG. 7 shows a cross section through the joint according to the lineVII, VII in FIG. 6,

FIG. 8 shows, in an enlarged representation, a cross section accordingto FIG. 7 through the upper platform,

FIG. 9 shows an isometric representation of the lower platform,

FIG. 10 shows a view of the lower platform according to the arrow VI inFIG. 5,

FIG. 11 shows a cross section through the lower platform according tothe line XI, XI in FIG. 10,

FIG. 12 shows a cross section through the lower platform according tothe line XII, XII in FIG. 10,

FIG. 13 shows a plan view of the lower platform according to the arrowXIII in FIG. 10,

FIG. 14 shows an isometric representation of the upper platform,

FIG. 15 shows a view of the upper platform according to the arrow VI inFIG. 5,

FIG. 16 shows a plan view of the upper platform according to the arrowXVI in FIG. 15,

FIG. 17 shows a side view of the upper platform according to the arrowXVII in FIG. 15,

FIG. 18 shows a cross section along the line IIXX, IIXX in FIG. 16,

FIG. 19 shows a cross section along the line IXX, IXX in FIG. 16,

FIG. 20 shows a side view, corresponding to FIG. 7, of an attachmentelement for a stocking,

FIG. 21 shows a view according to the arrow XX in FIG. 20,

FIG. 22 shows a plan view of the attachment element according to thearrow XXII in FIG. 20,

FIG. 23 shows a bottom view according to the arrow XXIIV in FIG. 24,

FIG. 24 shows a cross section through the attachment element along theline XXIV, XXIV in FIG. 22,

FIG. 25 shows a view of a lever corresponding to FIG. 6,

FIG. 26 shows a side view of the lever,

FIG. 27 shows a wedge piece in a side view corresponding to FIG. 7,

FIG. 28 shows a face view,

FIG. 29 shows a plan view of the wedge piece according to FIG. 27,

FIG. 30 shows in a view, corresponding to FIG. 7, a piston section of acounterrecoil mechanism, and

FIG. 31 shows a plan view of the piston section according to the arrowXXXI in FIG. 30.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

It will be expressly noted here that the following description of thefunctional model is reversible in its patterns of movement. In thisrespect, an allocation of reference labels is largely interchangeable.

FIGS. 1 through 3 show a functional model of a joint according to theinvention in three different settings, where the lower platform 1 isheld in a fixed position.

Accordingly, drawings 2 and 3 show an upper platform 2 adjusted relativeto the platform 1.

The configurations of the platforms 1, 2 of the functional model are notexplained in detail here because these can in principle be designeddepending individually on the type of attachment of the prosthesis orthe connection to the upper leg.

The platforms 1, 2 are connected by at least two levers 3, 4 ofdifferent length which are each articulated at their ends on theplatforms 1, 2. The axes 5, 6 of the lever 3 and the axes 7, 8 of thesecond lever 4 are perpendicular to the plane of the drawing. Thisallows the joint a relative swiveling of the upper platform 2 toward thelower platform 1 from the rest position shown according to FIG. 1 to aposition of maximum excursion according to FIG. 3, during whichswiveling the distance between the platforms 1, 2 is immediately reducedwith an excursion from the rest position according to FIG. 1. If weconsider the path traveled by the axis 6, it will in fact be seen thatthe latter, because of the connection via the lever 3 and the axis 5 onthe lower platform, moves downward on a circular trajectory 9, see alsoFIG. 4.

Because of the constructional design, the instantaneous center ofrotation during swiveling lies inside the joint, and a very naturallyacting function is thus obtained.

The illustration according to FIG. 4 also shows that, in the restposition shown in FIG. 1, the joint should not swivel much furtherbeyond this position. Since a further excursion of the lever 3 in FIG. 4to the left is not possible, because the distance between the axes 6, 8would need to increase upon further lowering of the axis 8 of the secondlever 4 on the circular trajectory 10, the upper platform 2, uponfurther swiveling, will turn into the joint, with appropriateconstructional design, in such a way that the top of the platform 2comes to lie lowermost.

In addition to dead-point positions, self-locking and self-retainingjoint positions, it is possible in particular for limit stops to fix therest position and/or the position of maximum excursion according to FIG.3. The run-in into these positions is expediently cushioned so thatthere is no hard impact on limit stops or no abrupt stop. For example,it is also conceivable to damp the angular velocity of the axes or toprovide suitable shock absorbers on the limit stops.

FIGS. 1 and 4 also show that, in the rest position, the lines 11, 12connecting the axes 5, 6 and 7, 8, respectively, of the levers 3, 4 areapproximately perpendicular to one another, i.e. the angle of opening βof the lines 11, 12 is approximately 90° in the illustrative embodimentand thus less than 95°. Moreover, in the rest position, the axis 8 lieson the connecting line 12 of the axes 5, 6 of the first lever 3, saidaxis 8 being arranged lying approximately centrally between the axes 5,6.

In the illustrative embodiment of the functional model, the first axes5, 7 articulated on the lower platform 1 are arranged substantially atthe same height, a horizontal line 13. In relation to this horizontalline 13, the angle of opening alpha of the line 12, and thus the settingof the lever 3 relative to the horizontal line 13, is approximately 52°,an angle alpha which lies in a range of 45° to 75°, preferably in arange of 50° to 60°, which range also describes the setting of heanterior cruciate ligament relative to a lower leg of a human knee.

However, in a variant (not shown) according to FIG. 1, a first axis of alever can also be arranged lying deeper than the first axis of the otherlever.

Correspondingly, the distance between the first axes 5, 7 of the levers3, 4 in the lower platform 1 can preferably be between 36 mm and 62 mm.The distance of the first axis 5 from the second axis 6 of the firstlever 3 articulated on the upper platform 2 also reflects the dimensionsof the articulation of the cruciate ligaments and their lengths in ahuman knee, where this distance is between 45 mm and 80 mm.

The distance of the first axis 7 from the second axis 8 of the secondlever 4 articulated on the upper platform 2 should then be between 27 mmand 62 mm, while the second axes 6, 8 in the platform 2 should be at adistance of between 16 mm and 62 mm. With such dimensions, it ispossible to ensure that the maximum excursion according to FIG. 3 isapproximately 140° and thus lies in a range of 130° to 150°, but whichpreferably reaches up to 175°, which largely corresponds to the possibleswiveling movement of a human knee.

As a result of these measures, the first and second levers 3, 4, atleast the respective connecting lines 12, 11 of the first and secondaxes 5, 6 and 7, 8, respectively, will at all times cross each otherduring swiveling, and the instantaneous center of rotation thus at alltimes lies inside the joint.

Moreover, in the rest position according to FIG. 1, the main weight loadaccording to the arrow 14 will cross the levers 3, 4 in such a way thatthe line of the load lies preferably between the second axes 6, 8, orpossibly slightly to the left in front of the axis 8 in FIG. 1. As aresult of this, a very stable stance is also achieved since it is onlywith an excursion of more than about 10° that the load according to thearrow 14 no longer intersects the connecting path between the secondaxes 6, 8 and thus has no inhibiting action on the joint.

It should be expressly noted here that the arrangement of the levers 3,4, for example also as double levers, is only illustrative. Thus, forexample, two first levers 3 can be arranged which lie outside of theplatform 1 on the end of the axis 5 and which also border the platform2. Alternatively, or in addition, it is equally possible to design thesecond lever 4 as a double lever, lying inside or outside of theplatforms 1, 2.

Moreover, for the function of the joint according to the invention, itis not important whether two second levers border ore or two firstlevers, or vice versa. If appropriate, arrangements can also be providedin which first and second levers are alternatingly arrangedperpendicular to the plane of the drawing.

By means of the joint according to the invention, a joint chain isobtained in which a first lever 3 is articulated in a platform 1 via anaxis 5, which first lever 3 is connected via an axis 6 to a second,upper platform 2. Lying inside the platform 2 there is a further leverarm, relatively immovable with respect to this platform, as a connectionto a further axis 8 on which a second lever 4 is articulated. At theother end, the second lever 4 is in turn secured to the lower platform 1via an axis 7. Extending inside the platform 1 there is a further leverarm which connects the first axes 5, 7 to one another. The particularkinematics of this joint are also based mainly on the dimensions of theindividual lever arms.

A preferred illustrative embodiment of a joint according to theinvention with brake and counterrecoil mechanism is explained in greaterdetail with reference to following FIGS. 5 through 31. For purposes ofgreater clarity, the previous position numbers will as far as possiblebe retained.

The joint shown in its rest position in FIGS. 5 through 7 is designedsubstantially symmetrical to its sectional plane according to FIG. 7. Ithas a lower platform 1 on which a double lever 3, 3′ is articulated onan axis 5 and on which a double lever 4, 4′ is articulated on an axis 7.The double levers 4, 4′ are each designed as angle levers, see alsoFIGS. 25, 26. At the other end, the levers, as has been explained, arearticulated on an upper platform 2 on axes 6, 8.

In the illustrative embodiment, the axes 5 through 8 are physicallyconstituted and are securely connected to the levers 3, 3′ and 4, 4′.The axes 5 through 8 are mounted so that they can rotate in mountings15, 16, 16′ of the lower platform 2, see FIG. 9. As a result, a brake ofthe type mentioned at the beginning can be provided for one axis, herethe axis 8.

The lower platform 1, see FIGS. 9-13, has a hollow cylindrical shaft 17through which a central seat 18 of circular cross section is defined,which is designed to be rotationally symmetrical with respect to anormal axis 19 which is substantially vertical in the rest position. Apiston section 20, see also FIGS. 30, 31, is mounted in the seat 18,and, adjoining this, a castellated nut 60 of a counterrecoil mechanism21 is axially spring-mounted and displaceable, see FIG. 7.

For this purpose, a sleeve 61 is introduced into the seat 18, and thepiston section 20 is guided in the sleeve 61 at one end. At the otherend, the piston section 20 passes through the castellated nut 60 whichitself can be guided directly in the seat 18. Arranged between thecastellated nut 60 and an annular shoulder 62 of the sleeve 61 there isa spring 63 whose pretensioning in the illustrated rest position of thejoint can be adjusted by adjusting the castellated nut 60 on the pistonsection 20.

A double lever 23, 23′ is articulated on the free end 22 of the pistonsection 20 lying opposite the upper platform 2, the articulation axis 24being parallel to the other axes 5 through 8.

At the other end, the double lever 23, 23′ is articulated on a shoulder25 protruding from the upper platform 2 and can swivel about anarticulation axis 26, again parallel to the axes 5 through 8. Theprotrusion of the articulation axis 26 from the upper platform 2 alreadylargely ensures an unimpeded swiveling of the joint. However, dependingon the excursion of the joint, it has also proven expedient for theupper platform 2 to be provided with recesses 27, 27′ for the levers 23,23′, see FIG. 14.

The shoulder 25 is designed separately in an approximately cuboid shapeand is received in a recess 28 in the upper platform 2. The depth ofinsertion of the shoulder 25 in the recess 25, and thus the distance ofthe articulation axis 26 from the platform 2, can be adjusted, forexample by means of a screw 29, which may also serve for securing. Inaddition, or alternatively, the shoulder 25 can be screwed to the upperplatform 2 also via bores 30, 30′.

When the load acting on the joint in the illustrated rest position isreleased, the force stored in the spring 62 will move the piston section20 of the counterrecoil mechanism 21 upward. The force will betransmitted via the shoulder 25 to the upper platform 2 by means of thedouble lever 23, 23′ articulated on the piston section 20, and the upperplatform 2 will swivel relative to the lower platform 1. In the restposition, the weight will generally be sufficient to tension the spring62 and to counteract the force of the spring 62. In the counterrecoilmechanism 21 too, a movement reversal is in principle possible throughanother choice of spring bearing.

The hollow cylindrical shaft 17 is also used to receive an attachmentpiece of a prosthesis (not shown). Joint and prosthesis are lockedtogether, for example, by means of a tensioning lock 31 covering anaxial gap 32.

In the preferred illustrative embodiment, a rotational movement of theaxis 8 is also provided which is slowed by a braking device of the typementioned at the outset.

For this purpose, the axis 8 is mounted in a mounting 33 in the upperplatform 2, said mounting 33 having a slit 34 which passes through theupper platform 2. In the illustrative embodiment, the mounting 33 istherefore limited to a simple axially slit tube. By reduction of the gapdistance, the axis 8 is braked frictionally in the mounting.

By continuing the slit 34 as gap 64 in the upper platform 2, a lever arm35 is formed via which the weight acts on the mounting 33. The weight isapplied via an attachment 36 known per se for example for a stocking ofthe prosthesis wearer.

The attachment 36 is part of a separately designed attachment element37, see FIGS. 20 through 24. This attachment element appears to be ableto swivel about a bolt 38 relative to the upper platform 2. The fact is,however, that by means of the special design of the bearing, see arrow39 in FIG. 8, between a contact angle 40 of the upper platform 2 and aback angle 41 of the attachment element 37, a swiveling relative to oneanother is made impossible. Since the rest of the attachment element 37stands free above the top side of the lever arm 35 of the upper platform2, the attachment element 37 acts, owing to flexural stresses, in themanner of a lever arm which, via a wedge piece 42, transmits the weightarising on the attachment 36 to the lever arm 35 of the upper platform2. The apparent axis of rotation of the attachment element 37 is hereessentially marked by a foot 43 supported in a corresponding recess ofthe platform 2.

The position of the wedge piece 42 transmitting force further, see FIGS.27-29, can be changed along the axis of the screw 44 provided for thispurpose in a recess 45 guiding the wedge piece 42 in the attachmentelement 37. In order also to be able to make adjustments to a finishedjoint, the attachment element also has, in the axial continuation of thescrew 44, a bore 46 which continues in a depression 47 of the contactangle 40 of the upper platform 2.

By displacement of the wedge piece 42, or of two wedge pieces relativeto one another, a prestressing can further be applied via the lever arm35 to the mounting 33, and a braking force can thus be preset inparticular for the rest position.

By changing the position and thus also the different angle setting ofthe top side of the lever arm 35 and of the attachment element, or byapplying different prestressing, and also the active length of the leverarm 35 which can be set as a result of this, it is possible to achievean individual adaptation of the response and characteristics of thebrake. This is assisted by a spring 48 which relieves the lever arm 35and whose pretensioning can be adjusted and which is held in a bore 49by an adjusting screw 50.

It may be desirable, however, for a rotational movement of the jointstill to take place when a large braking force is applied. For thispurpose, suitable measures, for example in the form of a slip clutch,can be provided between the axis 8 fixed by the brake and theconnections to the levers 4, 4′, or alternatively between the upperplatform 2 and the mounting 33. With suitable force application andsuitable choice of material, slipping may also occur within themounting.

This is achieved by the measure of connecting the levers 4, 4′ to theaxis 8 according to FIGS. 25, 26 by means of a seat 52 which has a slit51. Via a screw, bolt or the like introduced into a bore 53, it is thenpossible, by adjusting the slit width, to adjust in a characteristicmanner the forces transmitted from the connection of the levers 4, 4′ tothe axis 8. A further bore 54 is used to receive a fastening screw forthe mounting 33.

What is claimed is:
 1. A multiaxis prosthetic joint comprising a lowerplatform, and an upper platform which is connected to said lowerplatform by first and second levers having parallel axes of rotationwhich permit swiveling said upper platform from a rest position to aposition of maximum excursion relative to said lower platform, each saidlever having a pair of ends, each said lever being articulated at one ofsaid ends about a first axis on said lower platform and a second axis onsaid upper platform, wherein each said lever comprises a connecting lineconnecting respective said first and second axes, said connecting lineof said second lever being shorter than said connecting line of saidfirst lever, wherein said connecting lines of said first and secondlevers cross over each other at all times during swiveling between saidrest position and said position of maximum excursion.
 2. A multiaxisprosthetic joint as in claim 1 wherein said upper platform rotates aboutan instantaneous axis of rotation during swiveling of said platformsrelative to one another, said instantaneous axis of rotation lyinginside said joint.
 3. A multiaxis prosthetic joint as in claim 1 whereinsaid joint is one of self-retaining and self-locking in at least one ofsaid rest position and said position of maximum excursion.
 4. Amultiaxis prosthetic joint as in claim 1 further comprising at least onestop for fixing at least one of said rest position and said position ofmaximum excursion.
 5. A multiaxis prosthetic joint as in claim 1 furthercomprising means for cushioning run-in into at least one of the restposition and the position of maximum excursion.
 6. A multiaxisprosthetic joint as in claim 1 wherein said connecting lines of saidfirst and second levers form an opening angle of less than 95 degreeswhen said joint is in said rest position.
 7. A multiaxis prostheticjoint as in claim 1 wherein second axis of said second lever lies onsaid connecting line of said first lever when said joint is in the restposition.
 8. A multiaxis prosthetic joint as in claim 1 wherein thefirst axes are arranged at the same height when said joint is in therest position.
 9. A multiaxis prosthetic joint as in claim 1 wherein thefirst axes are arranged at the different heights when said joint is inthe rest position.
 10. A multiaxis prosthetic joint as in claim 1wherein said connecting line of said first lever forms an angle ofbetween 50 and 60 degrees with a line connecting said first axes whensaid joint is in the rest position.
 11. A multiaxis prosthetic joint asin claim 1 wherein said first axes are separated by a distance between36 mm and 62 mm.
 12. A multiaxis prosthetic joint as in claim 1 whereinthe first and second axes of the first lever are separated by a distancebetween 45 mm and 80 mm.
 13. A multiaxis prosthetic joint as in claim 1wherein the first and second axes of the second lever are separated by adistance between 27 mm and 62 mm.
 14. A multiaxis prosthetic joint as inclaim 1 wherein said second axes are separated by a distance between 16mm and 46 mm.
 15. A multiaxis prosthetic joint as in claim 1 whereinsaid platforms can swivel through a maximum excursion angle of between130 degrees and 175 degrees relative to each other.
 16. A multiaxisprosthetic joint as in claim 1 wherein one of said first and secondlevers is a double lever.
 17. A multiaxis prosthetic joint as in claim 1further comprising a counter-recoil mechanism arranged between saidlower platform and said upper platform.
 18. A multiaxis prosthetic jointas in claim 17 wherein said counter-recoil mechanism is bound betweensaid second axes when said joint is in the rest position.
 19. Amultiaxis prosthetic joint as in claim 17 wherein said upper platformhas a shoulder protruding therefrom, said counter-recoil mechanismcomprising at least one lever articulated about an axis on saidshoulder.
 20. A multiaxis prosthetic joint as in claim 19 wherein saidshoulder is adjustably mounted on said upper platform so that theposition of said axis on said shoulder relative to said upper platformcan be adjusted.
 21. A multiaxis prosthetic joint as in claim 19 whereinsaid lower platform has a central seat receiving an axiallyspring-mounted piston having a free end, said at least one lever of saidcounter-recoil mechanism being articulated at said free end.
 22. Amultiaxis prosthetic joint as in claim 1 further comprising at least onebrake for slowing down rotational movement of said upper platform aboutat least one of said second axes.
 23. A multiaxis prosthetic joint as inclaim 22 wherein said brake comprises a weight which generates a brakingforce loading said joint.
 24. A prosthetic joint as in claim 23 whereinone of said first and second axes is journaled in a mounting having anaxial slit.
 25. A prosthetic joint as in claim 24 further comprising anactive lever arm, said weight acting on said mounting via said activelever arm.
 26. A prosthetic joint as in claim 25 wherein said activelever arm is adjustable.
 27. A prosthetic joint as in claim 23 wherein abrake force can be preset when said joint is in said rest position. 28.A prosthetic joint as in claim 23 further comprising a spring whichcounters the braking force generated by said weight.